In a power transistor such as a trench-type insulated gate bipolar transistor (IGBT), a barrier layer is often formed below emitter layers and contact layers between trenches to improve the carrier injection enhancement effect (IE effect). However, the barrier layer has problems that holes cannot easily pass through the barrier layer, and that the barrier layer causes submerged resistance when the holes pass through the barrier layer. This results in an increase of loss at a turn-off of the power transistor and a decrease of latch-up strength of the power transistor.